1. The Field of the Invention
The present invention relates to improved multi-wheel assemblies, in particular, although not exclusively, for heavy transport vehicles. The invention also relates to a new or improved bead set band. The invention also relates to a method of retrofitting an existing wheel assembly with a modified design.
2. The Relevant Technology
Demountable rims and wheels are commonly mounted in due configuration on rear axle(s) on heavy duty vehicles such as earth moving trucks and trailers typically used in the mining industry. There are also some applications, though comparatively rare where the tires in dual mounted configuration are found on front axles of heavy equipment. The current wheel and rim design as applied to a dual wheel/rim situation is shown in FIG. 1. A segment of the rim base 10 is shown in cross section. The rim base 10 is made up of a front portion 12 a middle portion 14 and a rear portion 16. Each of these portions is formed by rolling and machining and then the three portions are circumferentially welded together to form the finished rim base 10. A wheel disc can be welded onto the inner diameter of the rim base.
The rear portion 16 has a radially outer surface 18 which is ramped radially outwardly in the direction towards the rear edge 20. The rear edge 20 also has a flange projecting radially outwardly. To provide additional support to the tire, an annular flange 22 is provided. The diameter of the radially outer periphery of the rear edge 20 is greater than the inner diameter of the tire wall. Accordingly, the rear tire wall is not permitted to pass beyond the rear edge 20 as the outside of the rear tire wall sits against and maintains an outward force on the annular flange 22.
At the front portion 12 of the rim 10, the radially outer periphery is provided substantially level with middle portion 14. The tire 24 is assembled onto the wheel rim by being passed over the front portion 12 until the back wall abuts against the rear edge 20 indirectly through the annular flange 22. The front wall of the tire 24 is held in position by the use of an annular bead seat band 26. The bead seat band 26 has a ramped radially outer periphery with a peripheral flange 28 projecting radially outwardly. The bead seat band 28 is held in place by a lock ring 30. An annual flange 32 is also inserted between the front tire wall and the peripheral flange 28.
In a dual wheel assembly, two such wheels or rims would be located side-by-side, with the lock ring 30 of each wheel or rim adjacent the lock ring 30 of the other wheel or rim see (FIG. 2). In order to change the tire of the inner wheel or rim, it is necessary to remove the outer wheel or rim to gain access to the inner wheel or rim. To change the tire of the inner wheel or rim, the tire is deflated and then the lock ring and bead seat band and flange are removed so that the tire can be removed. Once the tire has been changed, the flange 32, bead seat band 29 and lock ring 30 are returned, following which the outer wheel/rim can be returned to its position on the axle. For tires mounted on demountable rims, deflation of both outer and inner tire is required prior to loosening the cleat nuts for safety reasons.
To change the tire of the outer wheel or rim, the wheel or rim must first be removed from the truck. Once removed from the truck it is normally placed horizontally on the ground, the tire is first deflated and then the lock ring and bead seat band and flange are removed so that the tire can be removed. Once the tire has been changed, the flange 32, bead seat band 28 and lock ring 30 are returned, the inner wheel/rim can be returned to its positions on the axle. For tires mounted on demountable rims deflation of both outer and inner tire is required prior to loosening the cleat nuts for safety reasons.
The removal of the outer wheel rim to gain access to a tire of an inner wheel is time consuming. In particular, there are a large number of wheel nuts to be removed and later refitted from the outer wheel. When these wheel nuts are refitted, they are required to be retorqued to ensure adequate bond between the track axle and the wheel or rim. Furthermore, the lifting and removal of the outer wheel rim and later refitting has potential to damage the stud threads. Furthermore, the mere task of lifting the very heavy outer wheel rim has associated risks.
One prior art solution has been presented in Australian patent application No. 200126561 (see FIG. 3). This proposed solution involves reducing the size of the outer wheel rim so that the inner tire may be slid over the outer wheel rim without having to remove the outer wheel rim. To compensate for the decreased diameter in the wheel rim, thicker bead seat bands are used at both the front and the rear of the outer wheel rim. The different sizing of the outer wheel leads to introduction of additional parts including a new size for the wheel rim, a new sizing for the band seat bands, the locking-ring and “O” rings. In any situation where it is desirable to keep quantities of replacement parts in stock, the introduction of yet more parts in often remote locations and would seem to be a disadvantage. Fitting of heavy equipment tires has recorded many fatalities, accidents and near misses that were caused by mismatching of wheel/rim assembly components, the introduction of an “O” ring, lock ring, bead seat band and flange arrangement of different dimension and having specific application would only seem to increase the potential for mismatched components to be used with often tragic consequences.
Accordingly, it is an object of the present invention to address at least some of the aforementioned disadvantages or at least provide the public with a useful choice.
The foregoing prior art discussion is not to be taken as an admission of common general knowledge.